A common, yet generally unrecognized, problem with present day shock absorbers for automobiles, off road vehicles, race cars and motorcycles is that the rebound (extension) resistance necessary to control the stored energy of the spring is of critical importance. The higher the spring rate, the more rebound resistance is needed.
One approach to the overall problem of shock absorber design in the past is to provide for adjustable rebound resistance. A high degree of adjustability in both compression and extension resistance from the exterior of shock absorbers has been achieved in the dual adjustment through the piston rod of the shock absorber of our co-pending patent application, U.S. Ser. No. 07/270,010, filed Nov. 14, 1988 now U.S. Pat. No. 4,958,706 issued Sep. 25, 1990. In our further development, we have learned that a high degree of adjustability of the shock absorber is highly effective when the track or road conditions are predictable and when the mechanic making the adjustment is thoroughly familiar with the effects of the adjustment.
We have found that the full range of adjustability available employing our previous invention is far greater than needed for normal operation conditions. It also became apparent that fully automatic self adjustment of compression and rebound characteristics, responsive to actual traveled surface conditions is more desirable than manual adjustment for precise terrain conditions.
Attempts have been made to have computer controlled shock absorbers employing sensors, solid state computers which are preprogrammed and electrically operated valves controlled by the computer. As with any computer, its output is no better that the input and even though its speed of operation is indeed amazing, the overall system response including the mechanical valves determines the actual speed of the adjustment.
We have calculated that a vehicle traveling at the modest rate of 60 miles per hour will advance over the ground approximately 6 inches in 5 milliseconds. A computer controlled system which has an overall response speed in that range will not allow for effective compensation for surface conditions based upon any remote sensing of either present or anticipated road conditions. By directing optical or other sensors ahead of the vehicle the sensors incur the problems of dust or other conditions which may mask the true conditions and prevent effective computer controlled compensation.
Examples of computer or electronic controlled shock absorber systems are disclosed in the following patents:
______________________________________ 4,685,698 Klinkner et al August 11, 1987 4,651,290 Masaki et al March 17, 1987 4,648,622 Wada et al March 10, 1987 4,506,909 Makashima et al March 26, 1985 4,468,050 L. K. Woods August 28, 1984 and 4,634,142 Woods et al January 6, 1987 ______________________________________
One other approach is to employ inertial responsive valves which require no computer nor manual adjustment. Inertial responsive valves have been used in shock absorbers as typified by the following patents:
______________________________________ 3,127,958 H. T. Szostak April 7, 1964 3,696,894 Brady et al October 10, 1972 4,082,169 R. E. Bowles April 4, 1978 4,492,290 E. N. Zavodny January 8, 1985 Soviet Union 1,157,292 Kuzmenko et al May 23, 1985 ______________________________________
These inertial responsive valves give an indication that self contained systems which internally respond to accelerations can be used to provide automatic adjustment of orifices in shock absorbers. However these disclosed systems do not recognize any importance in reduction in rebound resistance in the presence of terrain defects, particularly dips nor do they provide inertia responsive rebound damping reduction.